What are paternity and maternity tests? 2026

The paternity or maternity test – to a lesser extent – ​​is usually requested for two reasons: either to prove that a child is yours or to prove that a child is not yours.

We talk about paternity tests because it is normally the potential fathers who request them since, in most cases, it is usually clear who the mother of the child is, except in some circumstances.

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The paternity test aims to determine, therefore, the first-degree relationship between the child and the possible father or mother.

What does the paternity test consist of?

The best way to perform it and the one with the greatest validity is genetic testing. In that sense, it is better to have it done in a public organization, such as the National Institute of Toxicology, which depends on the Ministry of the Interior. This is done to ensure that the results and the analysis itself have not been manipulated. Likewise, by doing it this way, we will avoid possible problems in the event of a hypothetical lawsuit.

We can divide this test, in turn, into two ways of performing it, one less invasive than the other:

• The first is through a blood test, both for the potential father and the child.
• The second way to do it is with saliva. With a small swab from the mouth, enough DNA is collected to determine the first-degree relationship.

The paternity test can be performed at any time, even while the baby is still in the mother's womb.

If you want to do it during pregnancy, it is very simple: it would be enough to extract a little amniotic fluid from the fetal sac and it can be done from the fifteenth week of gestation. On the other hand, a sample of chorionic villus, which is found in the placenta, can also be extracted.

The difference between paternity and maternity testing

There is a legal difference regarding the paternity test and the maternity test, which is given by the fact of having the consent of the person on whom the test is to be performed.

If you want to prove maternity.

If what you want to verify is paternity, the test can be performed without consent. In Spain the legislation does allow it and it would be worth providing an anonymous DNA sample to establish the relationship. This would not have legal validity, although it can be used for informational purposes.

For them to be valid, it is necessary to demonstrate that the DNA tests have been carried out on the alleged father or mother by presenting their identity, such as a DNI or a family book. Furthermore, before a trial, it is necessary that this evidence has preserved the chain of custody, that is, that it has not been altered at any time.

What the law says

If someone does not want to undergo this test, they cannot be forced – unless it is done without their consent, which would have no legal validity. However, if the person constantly refuses, the judge can force it to be done.

On the other hand, if the possible father had died, this test can also be performed on second or third degree relatives.

To present the evidence in a trial, it is necessary to present other evidence between those who would be the parents, such as photographs, messages, etc.

If a minor is involved in the process, his or her rights must be guaranteed. When the sentence arrives - a process that can last up to two years - and the paternity test is positive, the minor will have the right to: bear his father's surname, receive alimony and have what is due to him by inheritance. Furthermore, if the father requests it, he will have the right to a visitation regime. If the son is of legal age, he has the right to his legitimate inheritance and to bear his father's surname.